Modelling the role of consideration of alternatives in mode choice: An application on the Rome-Milan corridor

In this paper, we investigate the role consideration of the alternatives plays in mode choice models. On the Rome-Milan corridor, in Italy, where seven alternative modes of transport are available, we administered a stated choice (SC) experiment. Responses to supplementary questions on consideration of the different modes of transport and the presence of thresholds for the travel time attribute indicate travellers are less likely to consider the slower modes. Two model specifications, in which consideration for the slower alternatives is measured using both sets of supplementary questions, are proposed and contrasted against a model which assumes all alternatives are considered. Our results suggests that some of the unobserved preference heterogeneity could potentially be due to consideration effects. Accounting for consideration of alternatives also has direct impacts on choice probabilities, parameter estimates and willingness-to-pay measures

Investigation of a passive control system for limiting cavitation inside turbomachinery under different operating conditions

Abstract Herein, a new passive control system for limiting cavitation inside turbomachinery has been applied to a NACA0009 hydrofoil. The basic idea is to introduce slots nearby its leading edge, connecting pressure and suction sides of the hydrofoil, in order to increase locally the pressure on its suction side and to prevent cavitation from developing. The cavitating flow developed around a two-dimensional hydrofoil is here considered since it is an archetype of cavitation nearby the leading edges of the impeller vanes. Thus, the flow field developed at the leading edge of both the original and modified hydrofoil has been studied at different angles of attack in order to reproduce a wide range of operating conditions that occur inside turbomachinery. Eventually, a comparison of their performance in terms of polars (C L and C D ) and vapour volume fractions (α v ) is performed

Stated consideration and attribute thresholds in mode choice models: a hierarchical ICLV approach

Consideration of alternatives, as many other aspects related to the decision-making process, is not observable and challenging to measure. Even when supplementary information is collected during stated choice experiments, its use as an additional explanatory variable is discouraged due to potential endogeneity issues, measurement error and limited suitability for forecasting. To overcome these limitations, we propose an Integrated Choice and Latent Variable model where consideration of an alternative is treated as a latent variable. The novelty of the presented model is that the latent variable for consideration of an alternative itself is a function of another set of latent variables that represent thresholds applied by the decision maker to individual attributes (such as travel time and cost). The proposed hierarchical relationship between latent thresholds and latent consideration enables us to explain a share of otherwise purely random heterogeneity, and identify the structural drivers of consideration. The latter is of interest to policymakers and private operators

Development and experimental validation of kinetic models for the hydrogenation/dehydrogenation of Mg/Al based metal waste for energy storage

With the increased use of renewable energy sources, the need to store large amounts of energy will become increasingly important in the near future. A cost efficient possibility is to use the reaction of recycled Mg waste with hydrogen as thermo-chemical energy storage. Owing to the high reaction enthalpy, the moderate pressure and appropriate temperature conditions, the broad abundance and the recyclability, the Mg/Al alloy is perfectly suitable for this purpose. As further development of a previous work, in which the performance of recycled Mg/Al waste was presented, a kinetic model for hydro- and dehydrogenation is derived in this study. Temperature and pressure dependencies are determined, as well as the rate limiting step of the reaction. First experiments are carried out in an autoclave with a scaled-up powder mass, which is also used to validate the model by simulating the geometry with the scaled-up experiments at different conditions

Allowing for Heterogeneity in the Consideration of Airport Access Modes: The Case of Bari Airport

Mode choice models traditionally assume that all objectively available alternatives are considered. This might not always be a reasonable assumption, even when the number of alternatives is limited. Consideration of alternatives, like many other aspects of the decision-making process, cannot be observed by the analyst, and can only be imperfectly measured. As part of a stated choice survey aimed at unveiling air passengers’ preferences for access modes to Bari International Airport in Italy, we collected a wide set of indicators that either directly or indirectly measure respondents’ consideration of the public transport alternatives. In our access mode choice model, consideration of public transport services was treated as a latent variable, and entered the utility function for this mode through a “discounting” factor. The proposed integrated choice and latent variable approach allows the analyst not only to overcome potential endogeneity and measurement error issues associated with the indicators, but also makes the model suitable for forecasting. As a result of accounting for consideration effects, we observed an improvement in fit that also held in a validation sample; moreover, the effects of policy changes aimed at improving the modal share of public transport were considerably reduced

Resequencing Candidate Genes Implicates Rare Variants in Asthma Susceptibility

Common variation in over 100 genes has been implicated in the risk of developing asthma, but the contribution of rare variants to asthma susceptibility remains largely unexplored. We selected nine genes that showed the strongest signatures of weak purifying selection from among 53 candidate asthma-associated genes, and we sequenced the coding exons and flanking noncoding regions in 450 asthmatic cases and 515 nonasthmatic controls. We observed an overall excess of p values <0.05 (p = 0.02), and rare variants in four genes (AGT, DPP10, IKBKAP, and IL12RB1) contributed to asthma susceptibility among African Americans. Rare variants in IL12RB1 were also associated with asthma susceptibility among European Americans, despite the fact that the majority of rare variants in IL12RB1 were specific to either one of the populations. The combined evidence of association with rare noncoding variants in IL12RB1 remained significant (p = 3.7 × 10−4) after correcting for multiple testing. Overall, the contribution of rare variants to asthma susceptibility was predominantly due to noncoding variants in sequences flanking the exons, although nonsynonymous rare variants in DPP10 and in IL12RB1 were associated with asthma in African Americans and European Americans, respectively. This study provides evidence that rare variants contribute to asthma susceptibility. Additional studies are required for testing whether prioritizing genes for resequencing on the basis of signatures of purifying selection is an efficient means of identifying novel rare variants that contribute to complex disease

Genetic variability of the ABCC2 gene and clinical outcomes in pancreatic cancer patients.

Pancreatic ductal adenocarcinoma (PDAC) has an extremely poor prognosis, caused by various factors, such as the aggressiveness of the disease, the limited therapeutic options and the lack of early detection and risk markers. The ATP binding cassette subfamily C member 2 (ABCC2) protein plays a critical role in response to various drugs and is differentially expressed in gemcitabine sensitive and resistant cells. Moreover, single nucleotide polymorphisms (SNPs) in the gene have been associated with differential outcomes and prognosis in several tumour types. The aim of this study was to investigate the possible association between SNPs in the ABCC2 gene and overall survival (OS) in PDAC patients. We analysed 12 polymorphisms, including tagging-SNPs covering all the genetic variability of the ABCC2 gene and genotyped them in 1415 PDAC patients collected within the Pancreatic Disease ReseArch (PANDoRA) consortium. We tested the association between ABCC2 SNPs and PDAC OS using Cox proportional hazard models. We analysed PDAC patients dividing them by stage and observed that the minor alleles of three SNPs showed an association with worse OS [rs3740067: hazard ratio (HR) = 3.29, 95% confidence interval (CI) = 1.56-6.97, P = 0.002; rs3740073: HR = 3.11, 95% CI = 1.52-6.38, P = 0.002 and rs717620: HR = 2.90, 95% CI = 1.41-5.95, P = 0.004, respectively] in stage I patients. In patients with more advanced PDAC, we did not observe any statistically significant association. Our results suggest that rs3740067, rs3740073 and rs717620 could be promising prognostic markers in stage I PDAC patients

Meta-analysis of genome-wide association studies of asthma in ethnically diverse North American populations.

Asthma is a common disease with a complex risk architecture including both genetic and environmental factors. We performed a meta-analysis of North American genome-wide association studies of asthma in 5,416 individuals with asthma (cases) including individuals of European American, African American or African Caribbean, and Latino ancestry, with replication in an additional 12,649 individuals from the same ethnic groups. We identified five susceptibility loci. Four were at previously reported loci on 17q21, near IL1RL1, TSLP and IL33, but we report for the first time, to our knowledge, that these loci are associated with asthma risk in three ethnic groups. In addition, we identified a new asthma susceptibility locus at PYHIN1, with the association being specific to individuals of African descent (P = 3.9 × 10(-9)). These results suggest that some asthma susceptibility loci are robust to differences in ancestry when sufficiently large samples sizes are investigated, and that ancestry-specific associations also contribute to the complex genetic architecture of asthma

Common germline variants within the CDKN2A/2B region affect risk of pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors (PNETs) are heterogeneous neoplasms which represent only 2% of all pancreatic neoplasms by incidence, but 10% by prevalence. Genetic risk factors could have an important role in the disease aetiology, however only a small number of case control studies have been performed yet. To further our knowledge, we genotyped 13 SNPs belonging to the pleiotropic CDKN2A/B gene region in 320 PNET cases and 4436 controls, the largest study on the disease so far. We observed a statistically significant association between the homozygotes for the minor allele of the rs2518719 SNP and an increased risk of developing PNET (ORhom = 2.08, 95% CI 1.05-4.11, p = 0.035). This SNP is in linkage disequilibrium with another polymorphic variant associated with increased risk of several cancer types. In silico analysis suggested that the SNP could alter the sequence recognized by the Neuron-Restrictive Silencer Factor (NRSF), whose deregulation has been associated with the development of several tumors. The mechanistic link between the allele and the disease has not been completely clarified yet but the epidemiologic evidences that link the DNA region to increased cancer risk are convincing. In conclusion, our results suggest rs2518719 as a pleiotropic CDKN2A variant associated with the risk of developing PNETs